1. Field of the Invention
The present invention relates to a semiconductor dynamic quantity sensor and a method of producing the sensor.
2. Description of Related Art
JP-A-2003-014778 corresponding to US 2002/0158293 A1 discloses an acceleration sensor to detect acceleration in a direction perpendicular to a substrate. The acceleration sensor includes a movable electrode and a fixed electrode to oppose to each other. The movable electrode and the fixed electrode are separated from the substrate. A dimension of the movable electrode is different from that of the fixed electrode in the perpendicular direction.
When the movable electrode is moved relative to the fixed electrode in the perpendicular direction, opposing area between the movable electrode and the fixed electrode is decreased, because the movable electrode is out of alignment with the fixed electrode. Acceleration in the perpendicular direction can be detected based on a capacitance decrease of a capacitor defined between the movable electrode and the fixed electrode.
JP-A-2006-266873 corresponding to US 2006/0213268 A1 discloses an acceleration sensor to detect acceleration in a direction perpendicular to a substrate. The sensor has a seesaw structure, and a capacitor constructed by a movable electrode and a fixed electrode is defined at each end of the seesaw structure. When the seesaw structure is moved like a seesaw, a capacitance difference is obtained between the capacitors defined at the ends of the seesaw structure. Therefore, a direction of the detected perpendicular acceleration can be determined to head upward or downward relative to the substrate.
However, the acceleration sensor disclosed in JP-A-2003-014778 cannot determine a heading direction of the detected perpendicular acceleration. When the movable electrode moves in a second direction opposite from a first direction, the decrease of the opposing area is the same as the movable electrode moves in the first direction.
Further, the acceleration sensor disclosed in JP-A-2006-266873 cannot detect acceleration in a direction other than the perpendicular direction. That is, multi-axis acceleration cannot be detected by the acceleration sensor constructed by a single detection element.
If plural detection elements are needed to detect the multi-axis acceleration, cost of producing the acceleration sensor may increase, and a size of the acceleration sensor may be large.